Conventional ink cartridges include a printhead integrated within the cartridge or alternatively comprise an ink supply separate from a printhead. In some instances, a printhead integrated within an ink cartridge fails prior to the ink supply being exhausted, forcing the consumer to replace the partially used ink cartridge. In other situations, commercial printers using industrial-type printheads may have to shut down their production when a printhead fails. This shutdown causes lost income from suspended production as well as increased maintenance cost for professional replacement of the failed printhead. In either case, a significant disruption occurs.
One type of printhead is a thermal fluid ejection device. In a thermal fluid ejection device, ink fluid is contained within a chamber overlying a resistor. By sending electricity through connected conductor elements, the resistor can be heated, which in turn causes the ink fluid immediately above the resistor to vaporize and expand. The ink above the growing vapor bubble is forced to exit the chamber through an orifice, which becomes an ejected drop of ink. The functionality of the thermal fluid ejection device is dependent on the resistor. If the resistor fails, then the thermal fluid ejection device ceases to operate correctly.